Recently, chemical amplification type DUV (deep ultra violet) photoresists have proven to be useful to achieve high sensitivity in processes for preparing micro-circuits in the manufacture of semiconductors. These photoresists are prepared by blending a photoacid generator with polymer matrix macromolecules having acid labile structures.
According to the reaction mechanism of such a negative photoresist, the photoacid generator generates acid when it is irradiated by the light source, and the main chain or branched chain of the polymer matrix macromolecule is cross-linked with the generated acid to form a cross-linked structure. Thus, the portion exposed to light cannot be dissolved by developing solution and remains unchanged, thereby producing a negative image of a mask on the substrate. In the lithography process, resolution depends upon the wavelength of the light source--the shorter the wavelength, the smaller the pattern that can be formed. However, when the wavelength of the light source is decreased in order to form a micro pattern [for example, in the case of using 193 nm wavelength or EUV (extremely ultraviolet) light], it is disadvantageous in that the lens of the exposing device is deformed by the light source, thereby shortening its life.
Melamine, a conventional cross-linker, has a limited number (three) of functional groups which can form a cross-linkage with acid. Further, a large amount of acid must be generated when melamine is used as a cross-linker, because acid is consumed by the cross-linking reaction. As a result, high-energy light exposure is required for such cross-linking agents.
In order to overcome the disadvantages described above, chemical amplification type compounds that cross-link with a photoresist resin (also referred to herein as a "photoresist resin") and use less amounts of energy are desirable. However, such chemical amplification type cross-linkers have not yet been developed.